Cable infrastructure has been in place for quite some time now. Broadcasting radio frequency channels across coaxial cable provides cable television. This cable then connects directly to a television and allows channels to be received. Providing this service involved wiring communities with coaxial cable. To broadcast the television signal, the spectrum within the cables is divided into channels, with one station per channel broadcast on the cable from a central station. Due to the nature of coaxial cables, signal degradation and (where the signal on the cable begins to something) and interference (outside rf signals interfering with transmission) resulted in usage fewer channels than what was available on the cable.

Cable infrastructure has been in place for quite some time now. Broadcasting radio frequency channels across coaxial cable provides cable television. This cable then connects directly to a television and allows channels to be received. Providing this service involved wiring communities with coaxial cable. To broadcast the television signal, the spectrum within the cables is divided into channels, with one station per channel broadcast on the cable from a central station. Due to the nature of coaxial cables, signal degradation and (where the signal on the cable begins to something) and interference (outside rf signals interfering with transmission) resulted in usage fewer channels than what was available on the cable.

Revision as of 13:54, 4 January 2007

These pages are dedicated to the technologies that are used to connect to the Internet. They are organized by

Wire

Co-Axial Cable

Cable infrastructure has been in place for quite some time now. Broadcasting radio frequency channels across coaxial cable provides cable television. This cable then connects directly to a television and allows channels to be received. Providing this service involved wiring communities with coaxial cable. To broadcast the television signal, the spectrum within the cables is divided into channels, with one station per channel broadcast on the cable from a central station. Due to the nature of coaxial cables, signal degradation and (where the signal on the cable begins to something) and interference (outside rf signals interfering with transmission) resulted in usage fewer channels than what was available on the cable.

To reduce the length of the coaxial cable, the cable system began to be re-architected in the late 1990s by incorporating fiber-optic cables running to the neighborhood level. Once it reached the neighborhood, it would then be placed onto the coaxial cable already in place (with repeaters to ensure the signal wouldn’t degrade). This architecture, known as the Hybrid Fiber-Coaxial (HFC), shortened the length of the coaxial cable needed to deliver service to the home. This in turn allowed for use of more channels within the coaxial cable. With these extra channels, cable systems could begin to offer advanced services, including Digital Cable, High Definition Television (HDTV), Video on Demand (VOD) and, most importantly data transmission to connect to the Internet.

To connect to the Internet the Data Over Cable Service Interface Specification (DOCSIS), was developed. The specification calls for a modem at the consumer end and a Cable Modem Termination System (CMTS) and the cable providers end. The current specification in use allows for transmission of up to 40 Mbps downstream and 30 Mbps upload per channel in use. However, every customer does not realize this full speed, as bandwidth on the coaxial cable is shared by many homes (approx. 500 homes per cable) back to the fiber optic interface. To ensure that one household does not consume the entire bandwidth, individual cable modems are capped at a maximum speed, which in turn allows a cable company to charge more for faster access. Further, speed is also dependent on how many people are using the data channels at a given time. This creates an interesting dilemma. The first adopters found cable Internet to be fast and reliable, but found that their connection gets slower over time. The specification provided standardization for the cable modem that would allow many manufacturers to make modems, reducing the cost of barrier to entry for cable Internet.